Table 4.
Comparing current guidelines with risk prediction model
| Statistics | English data: total No postpartum women=433 353; total No VTE events=312 (imputed results) | Swedish data: total No pregnancies=662 387; total No VTE events=521 (imputed results) | ||||
|---|---|---|---|---|---|---|
| Women given thromboprophylaxis based on RCOG postnatal thromboprophylaxis guidelines* | Risk prediction model (England): top 35% cut-off (threshold=6.3 per 10 000 deliveries) | Women given thromboprophylaxis based on Swedish national guidelines† | Risk prediction model (Sweden): top 6% cut-off (threshold=18 per 10 000 deliveries) | Risk prediction model (Sweden): top 35% cut-off (threshold=7.2 per 10 000 deliveries) | ||
| Total No (%) postpartum women warranting thromboprophylaxis | 149 402 (34.5) | 149 402 (34.5) | 41 254 (6.2) | 41 254 (6.2) | 231 835 (35) | |
| Observed VTE events‡ | 197 | 212 | 109 | 158 | 355 | |
| Mean predicted risk per 10 000 pregnancies | 12.3 | 13.0 | 25.8 | 31.6 | 14.2 | |
| Sensitivity§, % (95% CI) | 63.1 (57.5 to 68.5) | 67.9 (62.5 to 73.1) | 20.9 (17.5 to 24.7) | 30.3 (26.4 to 34.5) | 68.1 (63.9 to 72.1) | |
| Positive predictive value¶, % (95% CI) | 0.13 (0.11 to 0.15) | 0.14 (0.12 to 0.16) | 0.26 (0.21 to 0.31) | 0.38 (0.32 to 0.45) | 0.15 (0.13 to 0.17) | |
| Specificity**, % (95% CI) | 65.6 (65.4 to 65.7) | 65.6 (65.4 to 65.7) | 93.8 (93.7 to 93.8) | 93.8 (93.7 to 93.9) | 65.1 (64.9 to 65.2) | |
*Women with either two low risk factors (varicose veins, age >35 years, overweight, body mass index (BMI) 30-39, parity ≥3, smoker, puerperal infection, elective caesarean section, multiple delivery, preterm birth, stillbirth, pre-eclampsia/eclampsia, or postpartum haemorrhage) or one high risk factor (comorbidities (inflammatory bowel disease (IBD), heart disease, kidney disease), BMI ≥40, or emergency caesarean section)).
†Women with two clinical risk factors (elective caesarean section, age ≥40 years, BMI ≥30, or any comorbidities (heart disease, IBD, or kidney disease)).
‡In women warranting thromboprophylaxis.
§Percentage of true positive venous thromboembolism (VTE) cases correctly identified on basis of current thromboprophylaxis guidelines/risk prediction model.
¶Percentage of women without VTE diagnosis correctly identified on basis of thromboprophylaxis guidelines/risk prediction model.
**Likelihood that women above treatment threshold will develop VTE.